C-reactive protein (CRP) concentration, serum/plasma

Why CRP Matters in Your Health

CRP is a marker for inflammation, which is your body’s way of responding to injury, infection, or illness. High levels may signal an active inflammatory process, such as an infection, autoimmune disorder, or other conditions causing tissue damage. This test is often used to guide treatment decisions or monitor chronic conditions like arthritis or heart disease.

When This Test Is Ordered

Your healthcare provider may order CRP testing if you have symptoms of inflammation (e.g., fever, pain, swelling), if you’re recovering from surgery or an illness, or if you have a chronic condition like heart disease, arthritis, or kidney problems. It can also be used to check for infections or to evaluate how well certain treatments are working.

What to Expect Before the Test

No special preparation is usually needed for this blood test. You may be asked to fast for 8–12 hours before the test if it’s part of a broader metabolic or liver evaluation. On the day of the test, avoid strenuous activity or smoking, as these can sometimes affect results. Bring any medications you’re taking to your appointment.

What the Results Mean

Results are typically reported in milligrams per liter (mg/L). A low CRP level may indicate no active inflammation, while a high level suggests inflammation is present. Your doctor will interpret the results in the context of your overall health and medical history. Very high levels can sometimes indicate severe infections or conditions like sepsis.